This same basic strategy – expressing the impact of our choices in quantities that really matter to us, rather than in quantities that don't – underlies The Norm Chronicles, a recent book by Michael Blastland and David Spiegelhalter that translates a plethora of everyday hazards into what they call "microlives". Really, this is just a fancy term for "half an hour of life"; a burger, they explain, knocks one microlife off the average adult's expectancy, as do two cigarettes. It's a clever way of adding immediacy to "chronic risks". Those risks, unlike skydiving or playing chicken on the railway tracks, that accumulate so gradually they're easy to ignore. Thinking in microlives also makes it evident that unhealthy, life-shortening choices can be balanced by life-extending ones: the first 20 minutes of exercise each day, for example, adds two. (Further minutes of exercise, sadly, are less beneficial.)

This would make for a fun or interesting mobile app. Perhaps it could link up to RunKeeper, Moves, Fitbit, or other activity tracking apps to keep a running tally of microlives for you. Run a few miles, earn enough microlife credits for a burger with all the fixings. Have a few extra beers and a cigarette on your weekly night out with the guys? You've just decreased the chance you'll see your grandchild graduate high school.